In a distribution system, a retailer or other product distributor (which may collectively be referred to as distributors) typically maintains an inventory of various items at one or more distribution centers, fulfillment centers, cross-docking facilities, materials handling facilities or warehouses (which may collectively be referred to herein as materials handling facilities). The inventory items are ordered from one or more vendors, received at the materials handling facilities as inbound shipments, and stocked in inventory of the materials handling facilities. In an order fulfillment process, orders for items may be received from customers of the distributor. Units of the ordered items are picked from various locations in the inventory in the materials handling facilities, processed for shipping, and shipped as outbound shipments to the customers.
The order fulfillment process may include a sortation process, in which mixed units picked for orders are sorted into their respective orders. For example, requests (e.g., orders) for items from requestors may be divided among multiple pickers, who then pick the items. The orders may be subdivided among the pickers; therefore, two or more of the pickers may pick items for one order. Consequently, a sort operation to select the proper units of items for given orders from the aggregations of units items returned by each respective picker is required. Conventionally, sorting may be performed using automated sorting mechanisms or manual sorting systems. Automated sorting mechanisms for sorting certain types of inventory items according to individual orders include, but are not limited to, the Crisplant® sorter, Eurosort® sorters, and automated sorting mechanisms offered by other vendors. Using an automated sorting mechanism, a stream of incoming picked items for multiple different customer orders are received at the automated sorting mechanism and sorted by the automated mechanism according to individual orders.
In typical automated sorting mechanisms, individual units of items are inducted from picked mixed items directly onto the sortation mechanism into carriers (e.g., tilt trays) that are fixed to the sortation mechanism. Thus, typical automated sorting mechanisms that are used in materials handling facilities tend to be linear sorting systems. Linear sorting inducts or places individual units of items from picked items (referred to as singulation) onto an individual tray or transport mechanism that is a fixed component of a linear piece of automated equipment. All of the trays or transport mechanisms are connected in a linear sequence (typically in a circle or oval continuously-running loop). An item is placed directly onto a carrier of the automated sorting mechanism. Linear sorting systems thus tend to be limited in velocity, total capacity, and the size and types of items that can be sorted.
Linear automated sorting mechanisms are typically expensive in both cost and floor area. Existing linear automated sorting mechanisms tend to not be flexible, and typically do not scale well as inventory throughput demands increase, since implementing a fractional solution is often impractical if not impossible. For example, to address a 30-40% increase in order throughput requirement may require purchasing an entire new sorting mechanism, effectively doubling throughput capacity despite leaving 60-70% of the new capacity unutilized, while also taking up at least twice as much floor space.
Shoe Sorters and Item Gridlock
The sliding shoe sorter is a high-speed automated sortation system for channeling and sorting medium size items, totes, and cartons. Operating at speeds up to 427 fpm, some shoe sorters can process as many as 9,000 pieces per hour depending on load length. Bi-directional shoes allow items to be offloaded from a sequence of moving items (e.g., in a continuously-running loop) to both sides of the sorter, improving space efficiency while providing greater design flexibility. However, if such offloading occurs at an insufficient rate, the shoe sorter may become gridlocked (e.g., unable to accept additional items for induction into the sorter) due to the quantity of items on the sorter.
While various embodiments are described herein by way of example for several embodiments and illustrative drawings, those skilled in the art will recognize that various embodiments are not limited to the embodiments or drawings described. It should be understood, that the drawings and detailed description thereto are not intended to limit embodiments to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of various embodiments as defined by the appended claims. The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims. As used throughout this application, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words “include,” “including,” and “includes” mean including, but not limited to.